Our long-range goal is to understand how the neural mechanisms for pursuit and saccadic eye movements operate in health and in various human disease states and how these motor mechanisms are related to higher-level functions. Although pursuit and saccades have long been viewed as distinct motor systems, recent work from our lab and others has shown that certain crucial processing stages are shared. This shared processing likely ensures that pursuit and saccades are properly coordinated with each other and with visual perception and cognition during normal behavior. The objective of this application is to increase our understanding of this functional overlap. In particular, we will examine the role of the frontal eye fields (FEF) in target selection for pursuit and visual judgments about visual motion, and compare the role of the FEF to that of the superior colliculus (SC). Our primary hypothesis is that some of the neural activity in the FEF is related to general estimates of target position and velocity that are agnostic about the eye motor output;consequently, these signals would be expected to support visual judgments as well as target selection for pursuit and saccades. The project will address the following three questions: (1) Does the SC contribute to the process of visual discrimination in addition to its role in target selection? (2) Does the FEF play a role in target selection for pursuit, and if so, how does this role compare to its contributions to visual discrimination? (3) Does the FEF contribute to the visual judgments involving motion? At the completion of this research, we expect to understand how activity in the SC and FEF is related to the mechanisms of target selection for pursuit, as well as saccades, and to have clarified the relationship between target and visual selection involving motion. The relevance of this research to public health. These studies are an important step toward understanding how the brain coordinates the components of voluntary movements and how it establishes and regulates the link between visual processing and motor control. These studies will therefore help refine clinical descriptions of the oculomotor system that are used to diagnose eye movement disorders in humans. Understanding how these systems interact will also help us understand how and why these circuits malfunction in a variety of developmental disorders.